The Eerie Silence Author:Paul Davies Publisher: Allen Lane ISBN:978-1-846-14142-3 Price: £25 (Hb), 240pp
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In the fiftieth year of the Search for Extraterrestrial Intelligence (SETI), Paul Davies’ book is a welcome wake-up call for the search for intelligent life elsewhere in the Universe. Davies, a professor at the BEYOND Center at the Arizona State University and a familiar name in popular science, has got to the nub of the SETI endeavour, highlighting the strengths and flaws of radio SETI (it is easy to do, but with marginally better than a cat in hell’s chance of finding anything) and exploring new frontiers where he believes we should be directing our search.

The Eerie Silence runs the gamut of SETI topics, from a brief overview of its beginnings, to ways we could possibly detect aliens, through to what happens after contact has been made. The latter is of growing interest to Davies who, in his role as chairman of the SETI Post Detection Task Group, has to seriously consider such issues, but it is the subject of the ‘shadow biosphere’ that really captures his attention. A shadow biosphere would consist of life on Earth with a separate origin to ourselves, a second tree of life hidden away in the microbial world. If the existence of a shadow biosphere could be proven, it would suggest that life can start easily, and repeatedly, on Earth-like planets, increasing the chances that life could also exist elsewhere.

Ironically, despite the title of the book, Davies doesn’t find the fifty years of silence eerie at all. It’s unlikely that ET knows we are even here to beam messages to, he argues, and suggests that radio beacons that ‘ping’ multiple worlds would be a better bet. Or perhaps ET has already been here, millions of years ago, and left some trace of their presence. The ‘twenty-first century SETI’ that Davies presents may be our best chance of finding out if we are alone in the Universe.

Keith Cooper